Dry electrolytic condenser



Sept' 29, 1942 c. M. BLACKBURN 2,297,608

DRY ELEGTROLYTI C CONDENSER Filed March 5, 1958 51 INVENTOR `electrodeassemblies and arrangements for Patented Sept. 29, 1942 DRY ELECTROLYTICCONDENSER Charles Marvin Blackburn, Jackson Township,

Brown County, Ind., assignor to P. & Co., Inc., Indianapolis, Ind.,

Delaware R. Mallory a corporation ot Application March 3, 19,38, SerialNo. 193,671

8 Claims.

This invention relates to electrolytic condensers and particularly toelectrolytic condensers of the dry type and electrodes therefor.

The present application is a continuation-inpart of my previously filedco-pending application, Serial Number 163,431, filed September 11, 1937.

An object of the invention is to improve the Udryl) electrolyticcondensers.

Another object is to improve Ithe method of making the electrodes andassemblies thereof.

Other objects of the invention will be apparent from the followingdescription and accompanying drawing taken in connection with theappended claims.

The invention comprises the features of construction, combination ofelements, arrangement of parts, and method of manufacture and operalionreferred to above or which will be brought out and exemplied in thedisclosure hereinafter set forth, including the illustrations in thedrawlng.

In the drawing:

Figure 1 illustrates diagrammatically a step in the manufacture of thecondenser electrodes;

Figure 2 shows an electrode produced thereby;

Figure 3 shows an electrode which has been further processed;

Figure 4 shows a modified form of electrode;

Figure 5 illustrates one way of arranging an electrode for assembly in acondenser;

Figure 6 shows another electrode arrangement;

Figure 7 illustrates a condenser assembly prior to winding;

Figure 8 represents another assembly; and

Figure 9 is a. section through a completed condenser.

A feature of the present invention resides in the novel method of makingthe electrodes. Another feature is the structural arrangement of theelectrodes themselves and a further feature is the method of assembly ina condenser unit.

While a preferred embodiment of the invention is described herein, it iscontemplated that considerable variation may be made in the method ofprocedure and the construction of parts without departing from thespirit of the invention. In the following description and in the claims,parts will be identified by specific n-ames for convenience, but theyare intended to be as generic in their application to similar parts asthe art will permit.

In the drawing Figure 1 shows the arrangement for producing theelectrode of Figure 2,

According to this arrangement a strip of cloth or gauze III or othersheet material of suitable characteristics and purity, and ofappropriate width for a condenser electrode, is led over a roller Ilalong with a second strip I2 of cloth or gauze, or other suitablematerial, and two parallel narrow strips of aluminum foil I3 and I4 sothat the foil strips are sandwiched between the gauze strips in spacedparallel relation.

'l'he sandwich assembly is then led over a second roller I5 andsimultaneously a backing layer I6 of paper (brown paper or cheapnewsprint is suitable) is led over roller I5 underneath the sandwichassembly. Paper I6 is somewhat wider than the gauze strips so as toprotect roller I 5.

As the sandwich assembly led over roller I5 a deposit I8 of film-formingmetal (preferably aluminum) sandwich assembly by metal spray gun I'I,commonly known as a Schoop gun, the metal being supplied to the spraygun as wire I9, melted by an Oxy-acetylene flame and sprayed onto thecloth. The gun may be oscillated back and forth across the sandwichstrip during spraying, if desired, to give a more uniform deposit. Dueto the porosity of the cloth or gauze the sprayed metal penetratesthrough the top gauze layer I0 and to some extent through the othergauze I2 where it is not protected by the narrow foil strips 3 and I4.The sprayed metal welds the foil strips to gauze I0 and, in so doing,develops a roughened or embossed surface on the back surface of thefoil.

The sprayed assembly is then carried forward with all layers incontiguous relation until it cools considerably after which it passesover a roller 20 where the paper backing I6 is carried off and the gauzebacking I2 is also stripped away from the front gauze I0 and foil stripsi3 and I4. Gauze I2, which has some metal deposited in it. 1s wound upin a roll and can subsequently be used for the front gauze in makinganother electrode.

Prior to the spraying operation a plurality of flattened aluminumterminals 2l are fastened to gauze l0. Terminals 2l consist of lengthsof wire which have been flattened for part of their The flattened partis laid across the cloth or gauze strip and a plurality of holes arepunched in the flattened portion so that the burr raised on thecloth-contacting side by the emergence of the punch projections extendsthrough the layer of cloth. The assembly is then rolled to flatten downthe burr onto the cloth and thus rivet the terminal thereto. In sprayingthe terhaving a spray-deposit A nlm-forming metal) on one side thereofand more minal becomes spray-welded to the gauze along with the foilstrips.

The resulting electrode is shown in Figure 2. It comprises a singlelayer of cloth or gauze Il I8 of aluminum (or other or less distributedthrough the layer, a pair of parallel foil strips I3 and Il integrallybonded to the cloth layer by the sentng a more or less embossed outersurface, and a iiattened terminal riveted and spray-welded to the cloth.

The terminals 2i can beattached at any desired spaced intervals alongthe cloth strip prior to spraying and after spraying the nishedelectrode may be cut to the required length, leaving one or moreterminals in each cut electrode strip. The terminals may be at the endor ends of the strip or at an intermediate point. It is alsocontemplated that the terminals may be attached after spraying, ifdesired.

The sprayed electrode, preferably before cutting into lengths, may befilm-formed by passing through a suitable bath of film-formingelectrolyte while applying A. C. or D. C. potential between theelectrode and the tank.

Two or more of the electrodes thus formed may then be wound up withinterposed porous sheet spacers of paper, cloth, regenerated sheetcellulose or other spacer materials suitable for dry electrolyticcondensers and impregnated with a suitable dry electrolytc condenserelectrolyte, such as one of those mentioned in my prior-filed co-pendingapplication, above identied. Due to the porosity of the spray-deposit,which is further enhancedby the gauze base, the electric capacity of thecondenser is several times that of a similar unit made of aluminum foilof the same dimensions. The electrolyte used for impregnation isabsorbed by the electrode gauze as well as by well as the front surfaceof the spray-deposit, is effective for increased capacity. The foilstrips I3 and I4, while serving principally to maintain a goodelectrical circuit longitudinal to the electrodes, also contribute tothe electric capacity, and due to the embossing or roughening of theexposed surface from the spraying operation, the capacity is stillfurther increased. Such a condenser is suitable for A. C. or D. C. uses.When used for D. C., the cathode may be` of foil instead of sprayedgauze, if desired.

spray-deposit and pretageously be used in multiple layers in formingcondenser electrodes. That is, instead of using a single electrode stripfor an electrode, as has heretofore been the practice, two or morestrips are placed face-to-face and their terminals connected together. Ihave found that the electrode produced from two strips put together inthis manner has substantially twice the effective capacitance of asingle strip. Three strips give three times the capacitance, etc. Thisis due to the fact that the layers are porous and when impregnated withelectrolyte permit a current path through the electrolyte to all partsof the several layers. The series resistance, due to the longer currentpath through the electrolyte, is increased somewhat by this arrangementbut is Well within acceptable commercial limits.

It will be noted that by this expedient, using a double electrode, onlyhalf the length of spacer material is required of what was formerlynecessary. And where the condenser is intended for D. C. uses, in whichcase the cathode plate may be a single thickness of foil or sprayedgauze, the amount of cathode material required is correspondinglyreduced.

Figure 5 illustrates a preferred method of producing this construction.This comprises folding the electrode of Figure 2, 3 or 5 back uponitself to form the double layer, the fold preferably being made near thetab 2 I The foil strips I3 and I4 should preferably be on the inside.

Figure 6 illustrates how three electrode strips might be placedface-to-face and attached together by their terminal tabs 2l, which areriveted or punched together at 25.

the spacers and hence the back, as

According to a modication the electrode of y Figure 2 is run through thespraying process a second time with the foil side nearest the spray gun.This applies a spray deposit to the exposed surface of the foil stripsand adds further sprayed metal to the gauze, thereby giving a stillhigher capacity. The modified electrode thus produced is shown in Figure3. Another advantage in this electrode resides in the fact that the foilis covered on both sides with sprayed aluminum and hence a lower purityfoil can satisfactorily be used than would be required where the foilitself is in contact with the electrolyte.

Figure 4 shows another modification in which a pair of narrow strips offoil 22 and 23 are laid in staggered relation on the two faces of astrip of gauze 24 and the assembly is sprayed on both sides to form an'integral electrode. The thin aluminum foil is simultaneously embossedby the spray in the design of the cloth backing.

I have discovered that the electrodes above described, as well as thosedisclosed in my above identified copending application, may advan-Figure I shows a D. C. condenser assembly 4made up using the electrodeof Figure 5 as an anode with a foil electrode 26 (having terminal 21) asa cathode and spacers 28 of paper, cloth or other suitable material,laminated if desired, between the anode and cathodes. The assembly canbe rolled up, impregnated with electrolyte,

and inserted in a suitable can according to weilv known procedure. Dueto the multi-layer nature of electrode I0 it is more flexible than a.single thick layer would be and the individual layers will slide on eachother during winding. Hence undue bre stresses and resultant crackingare avoided.

In some cases it is desirable to make a condenser having a commoncathode and two or more anodes, one of which is required to be of onlysmall capacity and which serves as an audio byfpass condenser in certaincircuits. Because of the extremely large capacities per unit areaobtained with sprayed electrodes a very small section of electrode stripwould be required for this by-pass condenser. While it is feasible touse such a section it introduces some mechanical handling diiiiculties.I have found that it is of advantage to use a piece of plain or etchedaluminum foil for the smallcapacity unit. The'- amount of foil required,while greater than the amount of sprayed gauze which would be necessary,is still very little. Moreover the use of foil gives a somewhat betterpower factor on these smaller units.

Figure 8 illustrates a condenser assembly comprising an anode I0 ofsprayed gauze, a second anode 30 of foil, and a common cathode 32 offoil separated from the anodes by spacers 33. Instead of common cathode32, two foil cathodes can be used, one Opposite each anode.

It is preferred that the assembly be wound by starting at the right-handend as indicated by the arrow. It will be noted that this rollselectrode I so that its top sprayed surface 34 is on the inside ofconcave face of the turns. This tends -to press the particles of sprayedmetal to.- gether and insure the highest conductivity parallel't'o thesheet. This is of particular advantage with the electrode of Figure 2wherein only one side is sprayed.

Figure 9 shows a completed condenser comprising a can 39 containing aroll 35 produced by rolling up the assembly of Figure 8. Anode terminals2| and 29 are brought up through insulating top 36 and provided withlugs 31 and 38, and the cathode terminal is inserted between the top andthe can and spun under the edge of the can.

While the present invention, as to its objects and advantages, has beendescribed herein as carried out in specific embodiments thereof, it isnot desired to be limited thereby but it is intended to cover theinvention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An electrode for dry electrolytic condensers comprising a layer ofbrous material, a terminal riveted thereto, and a deposit of hlm-formingmetal on and in said fibrous layer, saidfspraydeposit also bonding saidterminal thereto.

2. An electrode for dry electrolytic condensers comprising a strip ofcloth, a metal terminal strip laid transverse of said-cloth strip andattached thereto .by integral upset metal projections, and aspray-deposit of film-forming metal on and in said cloth and furtherbonding said terminal thereto.

3. 'I'he method of making an electrode for dry electrolytic condenserswhich comprises securing a terminal strip across a strip of brous sheetmaterial by punching through said terminal strip and said fibrous stripand flattening the projections thus produced on said terminal once ontosaid brous sheet surface, and then spraying a deposito! nlm-formingmetal onto said fibrous sheet.

4. The method of 'making an electrode for dry electrolytic condenserswhich comprises running together two strips of cloth with at least onenarrower strip of metal sandwiched therebetween, spraying a deposit offilm-forming metal into one side of the sandwich assembly whereby saidmetal strip is bonded to the cloth which is4 directly exposed to thespray and subsequently stripping oil the cloth not directly exposed tothe spray, and then spraying the foil side of the cloth strip to whichthe foil is attached.

6. An electrode for dry electrolytic condensers comprising a pair oflayers of open-mesh brous sheet material and a spray-deposit offilm-forming metal thereon and therein, said layers being disposed inface-to-face pressure contact and joined by a folded edge, and aterminal connected thereto.

7. 'I'he method of making an electrode for dry electrolytic condenserswhich comprises placing a thin aluminum foil against a backing having amultiplicity of closely spaced raised portions separated by depressionsand spraying the exposed surface of said foil with a deposit of aluminum to simultaneously emboss said foil and attach said depositthereto.

8. The method of making an electrode for dry electrolytic condenserswhich comprises placing a thin aluminum foil against a backing having amultiplicity of closely spaced raised portions separated by depressions,placing a layer of cloth over said foil and spraying a deposit ofaluminum into said cloth and against said foil to simultaneously embosssaid foil and attach said sprayed aluminum to said foil and said cloth.

CHARLES MARVIN BLACKBURN.

